Does an NBA team win the game if they have more three point attempts than the other team?

Introduction

Steph Curry is one of the best NBA players of all time and is also considered the best three-point shooter in the league. In the following text we deal with the topic of basketball with a focus on the three-point shot.

Critical Assessment of the Claim

This document contains the first home work assignment in the SBD2 module in the autumn semester 2024.

Claim

The statistical fact is that the claim in basketball is that if one team takes more 3-point shots per game than the other team, they win the game.

Related Article

My project is based on the claim of Scipiotheyounger, who says in his article that a higher volume of attempted 3 pointers has no influence on the victory. The article was published in December 2019 and compared the dates of all games in the 2018/2019 season, including the playoffs (total of 1307 games).

The analysis by Scipiotheyounger shows that the number of three-point attempts has hardly any influence on the game result. While three-pointers actually score more points than two-pointers, the number of attempts hardly influences the overall result or the probability of victory. Data from the 2018-19 season shows that the ratio of three-point attempts only explains 0.4% of the point differential in games. The team with more three-point attempts wins 50.8% of the time and loses 49.2% of the time. Interestingly, teams with more losses tend to shoot more threes, especially in the last quarter. This is because they do so out of desperation to catch up. To summarise, the data shows that more three-point attempts do not lead to more wins.

After reading through this article, the explanation and the conclusion were logical. I am a big basketball fan myself and follow the games in the NBA. Scipiotheyounger clearly explains in his article how he calculated the results, which makes the article accurate for me. He used a data set from the 2018-19 season, with all the games, which is understandable for me. In my eyes, it’s a small range, as this is only one season. But he also clearly explains that he is only referring to this one season. I do not think there is any bias in this article, because he is only referring to the data and basing his statements on the results.

However, upon further reflection, I question the claim because the three-point shooting revolution did not emerge until the 2010s. I wonder, what was it like before? Does this statement hold true for back then?

Based on this consideration, I think Scipiotheyounger’s claim may be true for the 2018/2019 season, but may be different for earlier seasons.

Related Dataset

I was able to find the dataset on Kaggle at the following URL: https://www.kaggle.com/datasets/szymonjwiak/nba-traditional

The data set consists of 68,120 rows and 29 columns. All boxscores of the NBA games between 1997 - 2024 are listed. There are two rows per game, one per team with the most important team stats. But I will only use the last twenty Seasons (2005 - 2024)

The dataset I use for my work is suitable because it lists data from the past 20 seasons. The selected assertion can be validated from the available data. In the Data set are no NA’s. With the diagnose_outliers() function I have detected 129 Outliers for the variable 3PA. But I am not going to ignore or clean them, because all of these games have their own stories. For example in one game there is a better defense for three point shots than in an other. Or a coaches decision can influence the three point shot attempts.

Data analysis

Total Games Won or Loss with more three point attemps

Let’s first take a look at the total of 25’738 games played over the past 20 seasons. I’ve created a new variable from the dataset that tells us whether the team with more attempted three-pointers won the game or not.

The bar chart below shows that the wins and losses are roughly equally distributed. There is a slightly higher number of defeats.

Based on this graph, we find that 48.8% of games are won when a team takes more three-pointers. In 51.2% of the cases, the team that took fewer three-pointers won.

Logistic Regression

As already described in the section above, the attempted three-pointers have no influence on victory or defeat. To prove this statistically, I have created a logistic regression

In this logistic regression, I find that the graph is significant because the p value is below 0.05.

## 
## Call:
## glm(formula = win ~ `3PA`, family = binomial, data = data)
## 
## Coefficients:
##               Estimate Std. Error z value Pr(>|z|)  
## (Intercept) -0.0492105  0.0241178  -2.040   0.0413 *
## `3PA`        0.0020151  0.0009193   2.192   0.0284 *
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
## 
## (Dispersion parameter for binomial family taken to be 1)
## 
##     Null deviance: 71361  on 51475  degrees of freedom
## Residual deviance: 71356  on 51474  degrees of freedom
## AIC: 71360
## 
## Number of Fisher Scoring iterations: 3

Correlation Matrix

So that I can still show a statistical validation in my project, I next create a correlation coefficient that shows how the two variables win and 3PA correlate. I also add the variable 3P%, as I am also interested in this.

I realise that the two variables win and 3PA do not correlate. It is astonishing how exactly they do not correlate, as the correlation coefficient is rounded to 0.01.

Analysis over the past 20 years

As described in part one, I suspect this has changed over the past few seasons as the three-point evolution has taken place.

This graph shows that the trend line (blue) has moved between 50.1% and 47.4% in recent years. This indicates that the value has not changed significantly over a long period of time and that the three-point evolution has had no influence on the winning percentage.

Volume of the 3PA in the past 20 years

As mentioned in the chapter above, a three-point shooting revolution took place in the 2010s. However, although teams in the modern NBA (from 2015) score significantly more points from three-pointers, this has no influence on winning.

In this chart, I illustrate the way teams score their points with yearly averages. This graph again clearly shows that a lot more three-pointers are being taken from 2015 onwards.

Storytelling

Connection between the claim and the dataset

The data set I found offers many possibilities to compare the past twenty seasons. The claim, which I described at the beginning, is whether a team with more three-point attempts in a game than the other also wins the game. I tried to find this out with different statistical results.

At the beginning, I only compared the wins and losses of the teams that took more three-point shots in a game. This gave me an overview that the total number is almost the same. This was also the case with the results of Scipiotheyounger’s article.Compared to the article, however, I have compared not one but 20 seasons, which means that my analysis covers a longer period of time.

I also created a logistic regression which compared the two variables 3PA and win. I used the logistic regression because the win variable is binary. The p value was less than 0.05 which indicates that it is significant. The results of this logistic regression indicate that the variable 3PA has a very small influence on the variable win.

Afterwards I created a correlation matrix, for me personally this result says the most. Because it is clear that the correlation between the variables win and 3PA is 0.01. This means that the more three-point shots attempted do not indicate whether a team wins.

I also compared that the winning percentage with more three-point attempts has only changed slightly in recent years. There is a slight downward trend. In my analysis, this is an extension of the article by Scipiotheyounger, as he only used one season as the data basis.

I also show the three-point evolution in more detail in the last diagram. This is to show how much the style of play in the NBA has changed in recent years. At the beginning I thought that the three-point revolution might have an influence on my claim, but this was not confirmed. It is interesting to note that no fewer free throws and two-point attempts are being taken, but the volume of three-point attempts has increased.

Limitation of the dataset

One limitation of this data set is that it is unclear how external factors influence the attempted threes. For example, the defense was changed during a game or good three-point shooters changed teams. Do three-point shooters play worse in foreign stadiums than in their own? I can’t answer any of these questions based on this data set. I would need a data set that contains detailed player information.

Conclusion

In this analysis, I focus on the data and whether or not the 3PA variable has an impact on the win. However, I think it is important to emphasise that basketball is played by humans. And people make irrational decisions or mistakes in pressure situations, like a basketball game is. This is normal, but is difficult to prove with data. However, I can confirm that Scipiotheyounger’s claim was confirmed by my analysis. I have proven that the attempted three-point shots have no effect on the win or loss.

In conclusion, it can be said that the claim, if one team takes more 3-point shots per game than the other team, they win the game, is not true.